In the pressure tube-piston devices, such as gas springs, the axial position of the piston and of a piston rod connected thereto can be continuously varied by opening a control valve passage and closing it again after the desired position has been obtained. Such pressure tube piston devices may be provided for positioning a secondary object with respect to a primary object. It is frequently desirable that in case of excess forces applied to the secondary object, the pressure tube-piston device is length variable due to an overload security function.
By such an overload security function damaging of the system comprising the first and the secondary object and the pressure tube-piston device can be avoided.